Transcript More on Characterization - Terp Connect

More on Characterization
• Qualitative size distribution dynamics
• Particle chemistry
•Particle chemical characterization
Size distributions may change over time
Starter size distribution:
Processes in which volume is conserved
Coagulation, communition or breakup, restructuring
Processes in which volume not conserved
Condensation, evaporation, nucleation, sedimentation,
In class project – changing shapes of distributions
Chemical composition not always same
Varying degrees of chemical homogenaity in particle mixtures
•Particles all of one chemical species (ie salt granules) –
chemically homogeneous
•Particles are all of one chemical species, but the particles are
mixed – externally mixed
•Particles are of two or more chemical components, but
composition of each particle is same – internally mixed
•Individual particles have different compositions
Chemical composition may vary with size
Pharmaceutical powders for inhalation - want small drug
particles mixed with and loosely bound to larger inert particles
Emissions from incinerators – some high volatility compounds
evaporate in high temperature zone and nucleate downstream
forming ultrafine high surface area particles
More examples
How to measure chemical composition?
Many techniques – survey of analytical chemistry
Some need large sample of material, so need to take average
over whole size distribution, and/or time
Some need extremely small amounts of material so
representative sampling is crucial
Some can tell you composition on-line or nearly on-line
Some require off-line analysis
SADK – secret acronym decoder kit
a. Atomic absorption spectroscopy (AAS)
b. Inductively coupled plasma- atomic emission
spectroscopy (ICP-AES)
c. Laser induced breakdown spectrometry (LIBS)
d. Time of Flight Mass spectrometry of aerosols (TOF-MS)
e. X-ray Fluorescence (XRF)
f. Proton Induced X-Ray Emission (PIXE)
g. Neutron activation analysis (NAA)
h. X-ray photoelectron spectroscopy (XPS)
i. Auger spectroscopy
j. X-ray diffraction (XRD)
k. Energy dispersive X-ray spectroscopy (EDX or EDS)
l. Electron energy loss spectrometry (EELS)
Analytical situations: in class problem